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P208 – A Novel Standard for Identifying Half Siblings Developed Based on Likelihood Ratio
As a gold-standard marker, STRs have been established to be powerful in kinship assessment. Meanwhile, the likelihood ratio (LR) calculation strategy, which is mentioned in the International Society for Forensic Genetics (ISFG) recommendation, is usually used in the STR system for kinship analysis. However, such a strategy suffers from misjudgments, and there is no systematic study of the situation in which misjudgments occur, the probability of their occurrence, or the type of such misjudgments. Here, we first simulated 10,000 half-sibling pairs for each of the 40, 60, 80, and 100 STRs. LR values were then calculated based on the ITO method and compared with five relationships simultaneously to evaluate the true positive rate (TPR) and the type of misjudgments. We next introduced a combination criterion named HRA standard to reduce the misjudgment rate and assessed the TPR at different thresholds in HS identification. Our results indicated that the TPR could reach at 98% to discriminate half-siblings from other kinships using ≥60 STR loci at a threshold of log10 (LR) = 4. While using the HRA standard at log10 (LR) = 4, the TPRs were all higher than 99%. Even a TPR of 99.9% for discrimination of HS from other close relatives can be achieved using the HRA standard. Our results provide a promising strategy and guidance applicable to complex kinship analysis. To improve the accuracy of the HRA standard in kinship analysis, further studies are needed to get extensive population genetic data, considering the mutation of loci and testing of true pedigree samples.
Authors
- Zidong Liu (School of Forensic Medicine,Shanxi Medical University, China)
- Bofeng Zhu (School of Forensic Medicine,Shanxi Medical University, China)
- Gengqian Zhang (School of Forensic Medicine,Shanxi Medical University, China)
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